When I first got chickens, (Me being inexperienced and all) I put them in a triangular coop and at night I would put them up in the roost area of it. One day I came down to the yard and they were all gone. There were no feathers or carcasses and barely any blood. All that was there was a shallow hole, maybe 4 inches deep and 7 across. Note- We live on top of a wooded hill, and at the bottom of that there is a swampy pond if that helps.